Can my toddler sleep in her rear facing car seat?

My daughter is 14 months and will not fall asleep on her own in the cot. She’s too heavy now for me to stand and rock her so I’ve started strapping her into her old rear facing car seat and rocking her to sleep – she goes off within 5 minutes. I leave her in the seat between 30 mins and an hour to make sure she’s in a deep sleep then transfer her to her cot. Are there any danger to her of me doing this or any health implications?

EOWYN